Posted
by
Soulskill
on Wednesday November 06, 2013 @01:10AM
from the it-all-comes-down-to-focus dept.

An anonymous reader writes "To boost its Wi-Fi capacity in packed lecture halls, Georgia Institute of Technology gave up trying to cram in more access points with conventional omni-directional antennas, and juggle power settings and channel plans. Instead, it turned to new high-gain directional antennas. They look almost exactly like the bottom half of a small pizza box, and focus the Wi-Fi signal from the ceiling-mounted access point in a precise cone-shaped pattern, covering part of the lecture hall floor. Instead of the flaky, laggy connections, about which professors had been complaining, users now consistently get up to 144Mbps (if they have 802.11n client radios). 'Overall, the system performed much better' with the new antennas, says William Lawrence, IT project manager principal with the university's academic and research technologies group. 'And there was a much more even distribution of clients across the room's access points.'"

Don't be silly. Enterprise kit is priced also because if done well the need for an expensive human to tend it goes down a lot -- despite often being complex and versatile pieces of kit. Of course, the margins are still quite huge and in that sense certainly overpriced.

But still worth it in the enterprise environment. There is a reason the likes of cisco can get away with 90%+ margins on hardware AND gouge you for support contracts. Compare and contrast how OpenWRT takes $60 consumer crap and gives it $600+-

Perhaps Georgia Institute of Technology has a big endowment, that they can afford to install such devices all over their campuses.

For most private enterprises, on the other hand, it's simply not affordable.

Most private enterprises have no need of this technology, because they don't have so many wireless clients packed into one location. Even the most happenin' Starbucks is an order of magnitude less dense than a lecture hall. This kind of technology would have application in crowded places that also

Every time I was in a crowded hall and someone tried that, it was hard for the student to be heard by the professor, next to impossible for students further out to hear, and by the time the interaction completed, I was often wondering if it was worth everyone else's time to have sat through the one person's words and the response to them. I can see the benefit of a large crowded hall if the school is maximizing the use of the time of a visiting guest lecturer. I went to a couple such symposiums I'm very g

Do that later. Maybe the prof can look something up. Maybe one or two students. But to require wifi connectivity continually for every single student in the lecture is misguided. That's anarchy. If students don't want to be there or think that it's a waste of time then they can just fork over their thousands of dollars and stay home.

Now start working on something to block wifi in lecture halls instead.

To absorb the RF energy -- b/g/n Wifi is very close to the frequency used in microwave ovens and so it's optimised to heat up meaty tissue (and vegetables too; this is Georgia Tech we're talking about, isn't it?)

It is hardly newsworthy that a group of IT network techs 'fixed' their coverage and performance problems using directional antenna technology.
Radio techs have been doing exactly that since they learnt about propagation.
A newsworthy story would be that they have (finally) started incorporating at least basic RF theory in all IT networking related courses and subjects.

It is hardly newsworthy that a group of IT network techs 'fixed' their coverage and performance problems using directional antenna technology.Radio techs have been doing exactly that since they learnt about propagation.

so... does this mean you aren't interested in the story about how they replaced the batteries in the remote?

I take it you've never actually been to a crowded lecture hall or conference room? There are thousands of these things with administrators that have no clue about this idea. It IS news to many people who are responsible for this exact sort of thing. It may not be news to you, but there have been many times where I was in a crowded area where I would kill for wifi, but it wouldn't work due to crowding.

I have, lamenting each time that our education system is releasing Network Admins into the wild with no RF knowledge. The story should have been...

We have now realise the error of our ways and are introducing compulsory RF Theory subjects to all our Networking courses.

Of course as others have said this is more marketing 'case study' by the antenna vendor than story. Notice TFA mentions that they did test antennas from other vendors, but give no indication of the relative performance. My bet is that most

In Europe we limit the maximum radiated power (EIRP). This means you'd have to drop TX power and the directional antenna helps on RX only. Still might be worthwhile.Although there is ample proof that WiFi don't have health issues, I still want to limit the EIRP. But to what level, I do not know. I think directional antennas currently have too strict a limit - you are not supposed to be standing next to a directional antenna anyway. OTOH people hardly understand what a 20dB antenna does (in TX).

With the antennas mentioned in the article, I agree.But for an example with +30dB antenna you could burn yourself. 1W +30dB is on the same ballpark as UNSHIELDED 1kW microwave oven.Sure, 30dB antenna is difficult to make, but 1W with 20dB should stay illegal.

It is a PASSIVE microstrip patch antenna. The gain adds to the TX as well as the RX.

The law doesn't care what sort of antenna it is -- the law specifies a maximum EIRP, and if you're already at that EIRP with a 6dB omni, your legal options are either (1) don't use a 12dB patch or (2) reduce your transmit power by 6dB to have the same EIRP.

In the US, at least, the FCC recognizes the benefit of highly directional antennas in that they reduce interference with other networks in the same channel, in every direction except where they're pointed, and therefore has established a "reward" for usi

The directional antenna on AP A only helps AP A on receive, not transmit.

However, there's substantial benefits in both receive and transmit when you change all the antennas from omnis to patches: The directional antennas on APs B, C, D and E prevent their transmissions from interfering with AP A's transmissions to AP A's clients, and likewise the directional antenna on A helps B, C, D, and E.

I think its funny how the summary says this like its some new fantastic technology. Directional gain antennae have been around almost since radio itself. There's nothing new about this, and if I had to guess, the ham radio club at Georgia Tech has been telling them to use directional antennae for a while now. Somebody with the authority to enact it managed to convince themselves that they though of it, did it, and now we're supposed to be impressed.

Directional antennas are not new. But configuring an array of directional antennas to precisely cover the seats in the lecture hall to minimize the number of users on any single access point is a new and novel way to deploy wireless access.

Deploying the same number of omnidirectional antennas in the same space would lead to massive overlap, interference, and clients unnecessarily switching between APs when they perceived a stronger signal from a different AP.

I haven't heard of a high density environment purposely set up this way therefor I think it is indeed newsworthy.

You're just saying that with your IT hat on. The reality is whenever you start doing some tricky stuff just hand over to the RF guys and they can do precisely this kind of coverage work with their eyes closed. It's quite basic to build a system like this, IFF you know what you're doing.

Wow, thank God for that. Good thing that we have slashdot to tell us that a university installed some standard equipment on their campus. Be sure to run an article when MIT replaces a couple of their switches next month.

I was told by a ham radio operator back in the day that a radio setup is only ever as good as its antenna system (and that includes the coax and feedline) to me this simply sounds like they finally listened to the old man in the crew.

They put 8 (or more) access points into a single unit, each with a directional antenna covering a segment of the room or venue. I looked at their product at a trade show or conference once (don't remember which) but it was way overkill for the spaces we had at the time which were separated with heavy reinforced concrete walls and floors, so needed an access point for each area.

It's always remarkable what people do with 802.11, but a lot of it strikes me as a mediocre standard being (over)extended with gimmicks.

Out of the box it works well enough for simple use, but more complex use cases (distance, density, broader coverage) seem to involve a lot of complexity to make up for the overall weakness of the standard (limited channel selection, radio power, etc).

Are there any changes on the horizon to generate new standards that would fix this? Such as designs tailored to high-density environments (hundreds or thousands of clients off a single radio), greater channel selections, better distance capabilities, etc?

I realize that not all of these may be something that works in a single product and that there are RF constraints that limit this, but at the end of the day the current 802.11 environment reminds me of DOS. Sure, with the right shims and magic you can run games (Quake, for the era) or a GUI OS on top of them, but there's something inherently hokey about it.

It's always remarkable what people do with 802.11, but a lot of it strikes me as a mediocre standard being (over)extended with gimmicks.

Out of the box it works well enough for simple use, but more complex use cases (distance, density, broader coverage) seem to involve a lot of complexity

Distance -- ye cannae change the laws of physics. You need one or more of: more power, more RF bandwidth, a higher gain antenna, or a coding system with less bits/s/Hz. Since you claimed power and bandwidth as problems below, I'll address them in a minute. You've already written off directional antennas as "gimmicks", and 802.11b already includes coding as low as 1Mb/s -- I don't think it's really worth putting even lower bitrates in the standard just so people can make >1 km links without having to spe

Hey, I'm not an RF guy and fortunately the equipment these days (controllers + radios) take away a lot of the low-level complexity in a way that mostly works. But even then the 2.4ghz band blows in high-density office spaces like office towers. There's just too much competition and you can't do much about the 20 other visible radios, all blasting out at maximum power to try to overcome each other.

That being said, it does still feel like a system designed for casual use (ie, a single AP allowing clients w

High gain directional antennas work better than low gain onni-directional antennas... Who knew?

Wasting 75% of your transmitted power by sending your signal out in a 360 degree radiation pattern instead of focusing all your power on a 90 degree 'wedge' is just stupid - I have to wonder who designed their wifi deployment, commission-based access point salesmen or results-oriented networking specialists?

so... if we all mounted our APs in the roof space with directional antenna pointed down we'd *all* have better wifi rececption. For me, my AP would be one layer of plasterboard worse off than where it is now (but with a gain from the antenna hopefully). I could use a Wok instead of an aerial change so it's cheap too.

This is exactly how high capacity AP's work. it has basically 4 (or more, I have seen some with 8) ap's that are connected to high gain antennas that segment off what they see. An advantage of high gain antennas is that they squish their signal and receive "window" into tighter lobes.

Honestly, if these people would take classes in RF design they would know this as the technology they are using has been around for decades, and the idea has been in use by companies covering large venues for at least a deca

When slashdot started some of the first stories here were about WiFi with directional antennas (eg. the famous pringles can long links). Long before I managed to get on the actual internet (instead of just a mere BBS) I knew people that were doing things with microwaves and directional antennas (microwave point to point link from a community radio studio to an FM transmitter). So is this story really just about somebody that actually decided to read up and get a clue about what were are doing instead of b

... a dedicated controller to handle the new “high density group” of access points; and the controller automatically handled configuration tasks like setting access point power levels and selecting channels.

Centralized management of the access points seems to be the solution, which doesn't require directional antennas to work.

Remember when we sent a man to the moon, and none of those scientists involved had access to wifi in their college lecture halls. People created the atom bomb without wifi, the first open heart surgery had no wifi enabled devices assisting, and we wrested fire from the gods on Mount Olympus without even a carrier pigeon. So why is it today that college students are unable to attend a lecture without needing connectivity? Sure, someone says they want internet access so that they can look up the material

The client-clients interference doesnt matter so much. Close clients are on the same AP/Channel and are thus participating in collision avoidance. Mid distance clients are on a different channel and thus dont interfere. Long distant clients who are on a re-used channel are so far away the signal is small (essentially noise), and the signal of the access point dominates such that SNR is still good.

From the AP end the directional parttern the antenna works in both directions. They transmit to only a limit

and in a professional manner works better than getting some intern who once set up a single ap for there parents to deploy a large scale wifi system - I am amazed i though wifi had magic unicorns that made it perfect!